A gas membrane-separation process is a process of separating acid gas such as carbon dioxide (CO2) from such mixed gas including at least acid gas as (i) synthesis gas synthesized in a large-scale plant that produces, for example, hydrogen and/or urea, (ii) natural gas, and (iii) exhaust gas. The gas membrane-separation process can save energy, and has attracted attention in recent years.
There have been proposed various gas separation membranes and membrane-separation apparatuses for use in the gas membrane-separation process. For example, Patent Literature 1 discloses a carbon dioxide separation apparatus, and Patent Literature 2 discloses a carbonic acid gas separation membrane.
A known example of an acid gas separation membrane element including a gas separation membrane is a spiral-wound acid gas separation membrane element. A spiral-wound acid gas separation membrane element includes (i) a wound body including a separation membrane, a feed-side channel component, and a permeate-side channel component that are wound in a laminated state around a core tube having a plurality of holes and (ii) a sealing section configured to prevent mixing of mixed gas (feed-side fluid) and permeation gas (permeate-side fluid).
Conventional spiral-wound acid gas separation membrane elements are structured such that (i) mixed gas flows in a direction crossed at substantially right angles by the direction in which permeation gas, which has permeated through a separation membrane, flows and that (ii) the core tube has, on a surface thereof, holes that are uniformly distributed so that the permeation gas can be collected into the core tube immediately. Further, conventional spiral-wound acid gas separation membrane elements are configured such that the core tube has a feed opening and a discharge opening both for a sweep fluid which serves to maintain the difference in partial pressure between acid gas in mixed gas and acid gas in permeation gas, which has permeated through a separation membrane, to improve the efficiency of separation by using the separation membrane.